This disclosure relates generally to the field of construction of wellbores through subsurface formations. More particularly the disclosure relates to methods for automatically calculating and displaying to drilling operations personnel values of drilling operating parameters that may optimize drilling of such wellbores and to characterize drilling performance on a specific wellbore with respect to benchmarks for such performance.
Drilling wellbores through subsurface formations includes suspending a “string” of drill pipe (“drill string”) from a drilling unit or similar lifting apparatus and operating a set of drilling tools and rotating a drill bit disposed at the bottom end of the drill string. The drill bit may be rotated by rotating the entire drill string from the surface and/or by operating a motor disposed in the set of drilling tools. The motor may be, for example, operated by the flow of drilling fluid (“mud”) through an interior passage in the drill string. The mud leaves the drill string through the drill bit and returns to the surface through an annular space between the drilled wellbore wall and the exterior of the drill string. The returning mud cools and lubricates the drill bit, lifts drill cuttings to the surface and provides hydrostatic pressure to mechanically stabilize the wellbore and prevent fluid under pressure from entering the wellbore from certain permeable formations exposed to the wellbore. The mud may also include materials to create an impermeable barrier (“filter cake”) on exposed formations having a lower fluid pressure than the hydrostatic pressure of the mud in the annular space so that mud will not flow into such formations in any substantial amount.
The drilling unit may have controls for selecting “drilling operating parameters.” In the present context, the term drilling operating parameters means those parameters which are controllable by the drilling unit operator and/or associated personnel and include, as non-limiting examples, axial force (weight) of the drill string suspended by the drilling unit as applied to the drill bit, rotational speed of the drill bit (“RPM”), the rate at which drilling fluid is pumped into the drill string, and the rotational orientation (toolface—“TF”) of the drill string when certain types of motors are used to rotate the drill bit. As a result of the particular values of drilling operating parameters such as the foregoing, the results may include that wellbore will be drilled (lengthened) at a particular rate and along a trajectory (well path) and may result in a particular measured pressure of the drilling fluid at the point of entry into the drill string or proximate thereto, called standpipe pressure (“SPP”). The foregoing are non-limiting examples of “drilling response parameters.”
Methods known in the art for optimizing drilling operating parameters are described, for example in the following publications:
International Patent Application Publication No. WO 2011/104504 which discloses a method for optimizing rate of penetration when drilling into a geological formation comprising the steps of: gathering real-time PWD (pressure while drilling) data; acquiring modeled ECD (equivalent circulating density) data; calculating the standard deviation of the differences of said real-time PWD and said modeled ECD data; calculating a predicted maximum tolerable ECD based on the calculated deviation; and determining the rate of penetration of a drill string based on the maximum tolerable ECD of a drilling process. In another aspect the present invention provides a system for optimizing rate of penetration, which system can be used to control the rate of penetration of a drill string based on the maximum tolerable ECD of a drilling process.
Canadian Patent No 2,324,233 which discloses a method of and system for optimizing bit rate of penetration while drilling substantially continuously determine an optimum weight on bit necessary to achieve an optimum bit rate of penetration based upon measured conditions and maintains weight on bit at the optimum weight on bit. As measured conditions change while drilling, the method updates the determination of optimum weight on bit.
International Patent Application Publication No. WO 2008/070829 which discloses a method and apparatus for mechanical specific energy-based drilling operation and/or optimization, comprising detecting mechanical specific energy parameters, utilizing the mechanical specific energy parameters to determine mechanical specific energy, and automatically adjusting drilling operational parameters as a function of the determined mechanical specific energy. A drill string includes interconnected sections of drill pipe, a bottom hole assembly, and a drill bit. The bottom hole assembly may include measurement-while-drilling or wireline conveyed instruments. Downhole measurement-while-drilling or wireline conveyed instruments may be configured for the evaluation of physical properties such as weight-on-bit. While drilling, weight-on-bit and calculate mechanical specific energy data are used to determine subsequent mechanical specific energy.
International Patent Application Publication No. WO 2013/036357 which discloses a method of evaluating drilling performance for a drill bit penetrating subterranean formation comprising: receiving data regarding drilling parameters characterizing ongoing wellbore drilling operations; wherein the drilling data at least includes mechanical specific energy (MSE); selecting a normalization MSE value, MSE0; normalizing MSE with the MSE0 value; and calculating a drilling vibration score, MSER.